CO2estimeter is a web extension to estimate the carbon impact of web browsing activity.
CO2estimeter has been tested for Firefox and Chrome.
It is not yet available on the official distribution channels of Firefox and Chrome. But you can install it manually by following the installation instructions for temporary extension installs in Firefox or unpacked extensions in Chrome.
Just download the archive for your browser from Releases and proceed according to the instructions that apply to your browser. If you are installing CO2estimeter for Chrome you need to unpack the archive first.
If you want to build the extension your self, clone this repository and run
pnpm install && pnpm run build:<firefox | chrome>The artifacts are created in the extension directory.
CO2estimeter uses the Sustainable Webdesign Model v4 (SWD) to calculate the CO2e value of green house gas emissions associated with browsing activity. For the calculations it uses the co2.js library from the Green Web Foundation.
The following section provides a short summary. The full picture can be found here.
There are many variables along the path of the packets you requested to load a webpage that contribute to the energy consumption of the page load. Taking into a account all these variables to get an estimate of the involved emissions, is unfeasible, may be also impossible. The SWD model thus breaks down this complexity by focussing on the number of bytes that are transferred over the wire (and air) to your device. The model uses data on the average energy consumption of three segments of the internet, data centers, network and user devices, to provide estimates for the average energy consumption per transferred byte. With these values it computes the estimated energy that is necessary to get, send and process the bytes to your device. Finally, the energy values are multiplied by the grid carbon intensity to get an green house gas emissions estimate in CO2e. The grid carbon intensity is the amount of CO2e emitted per kWh of electricity produced.
If you want to know more about the modelling choices, there is also this intersting article about the variance in estimates of CO2e emissions for internet activity
The SWD model comes with a couple of knobs. You can use different grid intensities for the different segments. You can also play around with an estimated green hosting percentage. In the context of the CO2estimeter, this is the percentage of data centers running on renewable or zero-carbon energy.
Of course, the approach has limitations. It does not take into account the energy consumption of the server that processes your request for example. Taken to an extreme, if your request causes a server to do some heavy work for a whole day but it only sends back a short message once it is finished, the estimated energy consumption of your request would just reflect the length of the short message, not the work the server has done. Also the distance that the requested data has covered on the way to your device does not have an effect on the estimates.
This extension leverages the Performance API that is available in browsers. It can continuously observe network requests and provide performance data about them. This also includes the so called transfer size. That is the size of the response as it is sent over the network to your device (as opposed to the decoded or decompressed size of the resource).
It is zero if the data was obtained from local cache or a CORS request. The size of requests is not tracked. If you are looking for an overview of how the Performance API can be used, check out this blog or Mozilla's docs. CO2estimeter collects this transfer sizes for all requests from a browser tab and attributes them to the domain of the page that is loaded in the tab. The data is stored in the local browser storage. You can delete it by pressing the "Reset" button of CO2estimeter in the top bar.
The comparisons of the estimated CO2e emissions are done with functions from the grasp package. For further information on its data check out its wiki page.